Human envenomations by Heloderma species are a rare but clinically important medical problem. We report a case of an adult male bitten on the left hand by a 50-cm male, captive specimen of Heloderma suspectum (Gila monster). Immediate signs and symptoms included pain at the bite site radiating into the arm and axilla and swelling of the hand and forearm. Systemic complaints of nausea, diaphoresis, and dizziness (without a decrease in blood pressure) lasted approximately 1 hour, and laboratory studies were normal. The patient's course was uneventful except for persistent hyperesthesia, which eventually abated. Two types of helodermatid bites produce distinct clinical pictures. The chewing bite potentially causes more envenomation than the slashing bite. The venom contains a number of protein and nonprotein components including serotonin, a bradykinin-releasing substance, protease, hyaluronidase, helodermin, and gilatoxin. The clinical presentation of a helodermatid bite can include pain, edema, hypotension, nausea, vomiting, weakness, and diaphoresis. No antivenin is commercially available. Treatment is supportive, and although first aid measures such as suction or compression may impede venom movement, they are unproved. Cryotherapy, tourniquet, and excision are dangerous and should not be used.